/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.view;

import java.util.Locale;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.lang.Nullable;

/**
 * Abstract base class for URL-based views. Provides a consistent way of
 * holding the URL that a View wraps, in the form of a "url" bean property.
 *
 * @author Juergen Hoeller
 * @since 13.12.2003
 */
public abstract class AbstractUrlBasedView extends AbstractView implements InitializingBean {

    @Nullable
    private String url;


    /**
     * Constructor for use as a bean.
     */
    protected AbstractUrlBasedView() {
    }

    /**
     * Create a new AbstractUrlBasedView with the given URL.
     *
     * @param url the URL to forward to
     */
    protected AbstractUrlBasedView(String url) {
        this.url = url;
    }

    /**
     * Return the URL of the resource that this view wraps.
     */
    @Nullable
    public String getUrl() {
        return this.url;
    }

    /**
     * Set the URL of the resource that this view wraps.
     * The URL must be appropriate for the concrete View implementation.
     */
    public void setUrl(@Nullable String url) {
        this.url = url;
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        if (isUrlRequired() && getUrl() == null) {
            throw new IllegalArgumentException("Property 'url' is required");
        }
    }

    /**
     * Return whether the 'url' property is required.
     * <p>The default implementation returns {@code true}.
     * This can be overridden in subclasses.
     */
    protected boolean isUrlRequired() {
        return true;
    }

    /**
     * Check whether the underlying resource that the configured URL points to
     * actually exists.
     *
     * @param locale the desired Locale that we're looking for
     * @return {@code true} if the resource exists (or is assumed to exist);
     * {@code false} if we know that it does not exist
     * @throws Exception if the resource exists but is invalid (e.g. could not be parsed)
     */
    public boolean checkResource(Locale locale) throws Exception {
        return true;
    }

    @Override
    public String toString() {
        return super.toString() + "; URL [" + getUrl() + "]";
    }

}
